bspeval.m

强大的nurbs的工具箱 nurbs曲线

function p = bspeval(d,c,k,u)
% 
% Function Name:
% 
%   bspeval - Evaluate a univariate B-Spline.
% 
% Calling Sequence:
% 
%   p = bspeval(d,c,k,u)
% 
% Parameters:
% 
%   d	: Degree of the B-Spline.
% 
%   c	: Control Points, matrix of size (dim,nc).
% 
%   k	: Knot sequence, row vector of size nk.
% 
%   u	: Parametric evaluation points, row vector of size nu.
% 
%   p	: Evaluated points, matrix of size (dim,nu)
% 
% Description:
% 
%   Evaluate a univariate B-Spline. This function provides an interface to
%   a toolbox 'C' routine.
nu = numel(u);
[mc,nc] = size(c);
                                                %   int bspeval(int d, double *c, int mc, int nc, double *k, int nk, double *u,int nu, double *p){
                                                %   int ierr = 0;
                                                %   int i, s, tmp1, row, col;
                                                %   double tmp2;
                                                %
                                                %   // Construct the control points
                                                %   double **ctrl = vec2mat(c,mc,nc);
                                                %
                                                %   // Contruct the evaluated points
p = zeros(mc,nu);                               %   double **pnt = vec2mat(p,mc,nu);
                                                %
                                                %   // space for the basis functions
N = zeros(d+1,1);                               %   double *N = (double*) mxMalloc((d+1)*sizeof(double));
                                                %
                                                %   // for each parametric point i
for col=1:nu                                    %   for (col = 0; col < nu; col++) {
                                                %     // find the span of u[col]
    s = findspan(nc-1, d, u(col), k);           %     s = findspan(nc-1, d, u[col], k);
    N = basisfun(s,u(col),d,k);                 %     basisfun(s, u[col], d, k, N);
                                                %
    tmp1 = s - d + 1;                           %     tmp1 = s - d;
    for row=1:mc                                %     for (row = 0; row < mc; row++)  {
        tmp2 = 0;                               %       tmp2 = 0.0;
        for i=0:d                               %       for (i = 0; i <= d; i++)
           tmp2 = tmp2 + N(i+1)*c(row,tmp1+i);  % 	tmp2 += N[i] * ctrl[tmp1+i][row];
        end                                     %
        p(row,col) = tmp2;                      %       pnt[col][row] = tmp2;
    end                                         %     }
end                                             %   }
                                                %
                                                %   mxFree(N);
                                                %   freevec2mat(pnt);
                                                %   freevec2mat(ctrl);
                                                %
                                                %   return ierr;
                                                %   }